Field of the Invention
The present invention relates to a method for the automatic characterization, preferably classification, of liver tissue in a region of interest of a liver of a living subject. The invention also relates to a characterization computer, in particular a classification computer, for the automatic characterization, preferably classification, of liver tissue on the basis of magnetic resonance images of the region of interest, and a magnetic resonance apparatus with such a characterization computer.
Description of the Prior Art
Liver disease is one of the most common causes of death. While the mortality rate for other diseases is falling, the incidence of liver disease is actually rising. One typical liver disease is hepatitis, which first causes inflammation that then changes to fibrosis and can later result in cirrhosis of the liver or liver cancer. Another problematic field is hemochromatosis (iron-storage disease) with which the body absorbs too much iron with the food. Here, once again, generally the liver is affected first and subsequently other organs, such as the pancreas or heart, are endangered. In the final stage, hemochromatosis can also result in cirrhosis of the liver or liver cancer. A further problem is the development of fatty liver disease.
Although, with usual precautionary checkups, a blood count generally also includes checks on various liver values, most liver diseases typically are only manifested at a later stage, and other symptoms also only occur once the disease has reached a significantly advanced stage. This greatly complicates treatment. In many cases, it is no longer possible to provide a cure.
Magnetic resonance scans are increasingly being used to obtain additional quantitative information about organs, such as the fat content. These values can then be used again as biomarkers for certain diseases. For example, like the blood count, in some circumstances, the values can also be used in clinical practice to determine the status of the disease or to monitor the course of treatment. Therefore, it would be desirable to be able to determine liver disease at a relatively early stage with the use of magnetic resonance images.
A disadvantage to doing so, however, is that generally the information about a specific disease is not contained in one single parameter that can be determined from the magnetic resonance images, but is presented in a combination of different parameters. It is also the case that different parameters can exert a mutual influence on one another. This relates to the determination of fibrosis in the liver. Although this can be identified by measurements using T1 images (i.e. T1-weighted images or by measuring the T1 values), since longer T1 relaxation times (spin-lattice relaxation times) can be indicative of more severe fibrosis, hepatic iron overload of the liver disadvantageously results in reduced T1 relaxation times. The outcome of this can be that, in patients with both hepatic iron overload and fibrosis, the fibrosis is masked by the hepatic iron overload and thus neither of the two diseases can be determined by the T1 measurement. Iron overload can also be indicated by measuring the T2 or T2* values (spin-spin relaxation times, wherein T2 relates to spin-echo methods and T2* to gradient-echo methods) or reciprocal values thereof.
To a certain extent, very experienced radiologists can also make assessments from individual analyses of the T1 images and T2 or T2* images or the reciprocal images thereof. However, this is always heavily dependent upon the experience of the diagnosing physician in question.
Therefore, it is suggested in the article by Banerjee R. et al. “Multiparametric magnetic resonance for the non-invasive diagnosis of liver disease”, Journal of Hepatology, 2014, Vol. 60, pages 69 to 77, that the T1 values first be converted to “cT1 values” (corrected T1 values), wherein the hepatic iron overload is included in the correction by the use of the T2 or T2* values. These “cT1 values” then permit assessments of the status of a possible fibrosis of the liver tissue.